When declarer cashes winners, forcing both defenders to discard, it is easy to take your eye off the ball. If both defenders throw the same suit they may give declarer an undeserved winner or two.
South’s weak 1NT opener is not classical – most would prefer to emphasise the strong spade suit. North’s raise to 3NT, ignoring the clubs, is sensible at pairs: there is no real prospect of slam in clubs, and 3NT outscores 5C if it makes an overtrick or two. Here 5C has no chance on a diamond lead, whereas 3NT makes on any lead.
West had an obvious non-diamond lead in the jack of hearts. Declarer saw 12 winners if both his long suits ran, so he won the ace of hearts, dropping the seven from hand, and started on clubs. On the third round he discarded a cunning queen of hearts, then all his diamonds, concealing the three of hearts. East threw all her spades, and West two diamonds and two hearts. Next declarer ran spades. East threw her two remaining hearts, then two diamonds, keeping the king-queen. West followed to the first three spades, then threw one more heart. On the last spade he had to choose between the ten of hearts and the ace of diamonds.
Who discards an ace? A defender who has been keeping track. East had shown an odd number of hearts at trick one, and played all three of them. Declarer, who had already produced 13 high card points, could not have the king of diamonds as well.